De-icing for gas turbines



April 12,1955 c. E. QUINBY ETAL DE-ICING FOR GAS TURBINES Filed June 28, 1951 6471-212. 6038,56 Zfirles E Qzzinfiy 451M 022' 718 zzvmvrom 67770RNY United States Patent DE-ICING FOR GAS TURBINES Charles E. Quinby, Ferndale, and Stanley M. Udale, Detroit, Mich., and Carl R. Giese, Cleveland, Ohio, assignors to Holley Carburetor Company, Detroit, Mich., a corporation of Michigan Application June 28, 1951, Serial No. 233,978

5 Claims. (Cl. 60-39.09)

The object of this invention is to prevent ice forming in the air entrance and thus wrecking a gas turbine.

Briefly, our invention includes a return passage from the rear to the front of the turbine so that hot gas can be recycled through the air entrance to melt any ice therein. A spring closed throttle in this passage is controlled by two variable factors:

1. Air fiowdynamic 2. Air pressure-static Two pairs of tungsten contacts in parallel in an electric circuit which includes a solenoid positively opens this throttle when either the pressure drops or the air flow fails. Two diaphragms separate these contacts and two springs normally keep the two pairs of contacts closed.

Fig. 1 shows diagrammatically in cross section elevation the preferred form of invention.

Fig. 2 is the front view of the grid and screen, the sub ject of this invention, taken on the plane 22 of Figure 1.

In the figures, is the air entrance, 11 is one of a series of vertical streamlined tubes located in the air entrance, immediately upstream of the screen 12. The tubes form a grid just immediately upstream of the screen 12. The tubes 11 are slotted at the back so that exhaust gases can impinge directly on the screen to melt the ice and can at the same time mingle freely with the air entering just before the air flows through the screen. 14 is the exhaust passage deriving its exhaust from the outlet 16 downstream of the gas turbine 18. 20 is the usual conical control located in the outlet 16. 22 indicates the usual burner in the combustion chamber. 24 is the shaft on which the turbine 18 is mounted. 26 is the blower mounted on shaft 24 and thus driven by the turbine, drawing air past the tubes 11 and through the screen 12 and delivering it to the combustion chamber 28 in which the burners 22 discharge. reflects air flow, chamber 32 being held at the impact pressure of the air leaving the compressor 26, and 34 is held at the low pressure obtained by lateral openings in as distinguished from the impact opening in the middle of Pitot tube 30 from which the high pressure from chamber 32 is derived. The diaphragm 36 located between the chambers 32 and 34 therefore refects the dynamic effect of air flow.

The effect of the high (static) pressure in the chamber 34 is imposed on the secondary diaphragm 38, the right side of which is exposed to atmospheric pressure. An adjustable compression spring 40 determines the lowest pressure at which this diaphragm 38 will respond to combustion chamber pressure. A similar adjustable spring 42 determines when the diaphragm 36 will respond to air fiow. p

A movable contact, preferably of tungsten, 44 engages with the stationary insulated tungsten contact 46 whenever the pressure in the chamber 34 is below a certain value. The movable tungsten point 48 is moved by the diaphragm 36 and engages the stationary insulated tungsten point 50 whenever the air flow is below a certain critical level. The conductor 52 when the manual switch 54 is closed conducts electrically from the battery 56 through the solenoid 60 and along the conductor 62 and the man ually operated switch 54 to the conductor 52.

A movable armature 64 is separated from the solenoid 60 by a spring 66. A rod 68 opens the balanced throttle valve 70 whenever electricity flows through the solenoid 60 which is whenever the manually operated switch 54 is 30 is a Pitot tube which "ice closed and whenever either of the pairs of tungsten contacts 4446 or 4850 is closed.

Operation During the normal operation of the gas turbine, both the pressure and the air flow are sufiiciently high and the springs 40 and 42 are adjusted to be sufficiently weak that the contacts 4446 and the contacts 4850 are held open. Spring 66 then holds the valve 70 in the position in which it is shown. In the event that ice forms on the grid 11, on the screen 12 or in the air entrance to the blower 26, the air flow is restricted and the Pitot tube 30 immediately reflects the lower air flow so that the contacts 4850 are closed by means of the spring 42 following immediately after a reduction in air flow. This reduction in air flow is also accompanied by a fall in pressure so that the contacts 44-46 are also closed. If either of these two paths of contacts are made active, current then flows from the battery 66 through the solenoid 60 to the conductor 62, pass the switch 54 to the conductor 52 and the current is grounded through the apparatus. The moment this happens, the armature 64 of the solenoid 60 is energized and the throttle valve rotates anticlockwise and exhaust is admitted through the passage 14 to the grid and the exhaust gases are discharggd over the screen 12 and the ice thereon is quickly mete Under some conditions of minimum speeds and loads, it may be possible that the valve 70 might be open during the slow speed, steady running of the device. However, the temperature would then be low and no harm would result from diluting the entering air with returned exhaust which would be recycled.

What we claim is:

1. In a gas turbine having the usual air entrance, a screen therein and an air blower downstream thereof, a combustion chamber downstream of said blower, a fuel entrance to said chamber, an exit for burnt gases, a turbine between the combustion chamber and said exit, a drive from the turbine to the blower and an exhaust outlet from said turbine, a non-icing device comprising an exhaust passage so located and connected so as to return some of the exhaust products from the exhaust outlet back into the air entrance adjacent to and upstream of said screen, a throttle valve in the exhaust passage, means responding to the formation of ice anywhere on the screen to reduce air flow and/or air pressure in said combustion chamber, to open said throttle so as to admit exhaust gases to the upstream entrance to said blower to melt the ice therein.

2. An ice melting device for a gas turbine having an air entrance protected by a screen comprising a plurality of perforated exhaust tubes located in front of said screen and discharging onto the surface thereof, a passage connected to the turbine outlet and to the inlet, a valve controlling the fiow of exhaust gases back through said passage from the outlet from said turbine to said tubes, means responsive to the fall of pressure in and/ or velocity through the said combustion chamber due to ice formation anywhere on the screen including a device responsive to air flow and/or pressure in the said combustion chamber to open said valve to admit said exhaust gas to said tubes to melt the ice on said screen when the air flow is restricted by the formation of ice.

3. In a gas turbine having the usual air entrance and an air blower therein driven by said gas turbine, a combustion chamber located downstream of said blower, an exhaust exit, a gas turbine located between the combustion chamber and the exhaust exit, a return by-pass leading the exhaust gases back to the air entrance, a throttle valve in said return by-pass, control means for said valve comprising a Pitot tube in the outlet from said blower, a diaphragm responsive to the differential pressures established by said Pitot tube, an electric switch controlled by said diaphragm, a solenoid connected to said valve to open the valve at low air flows, yieldable means to close said valve whenever the current is not flowing and the solenoid is not in operation.

4. An ice melting device for a gas turbine which comprises a passage for returning some of the hot gas to the turbine for recycling, a valve in said passage, 2. spring holding this valve shut, an electric solenoid adapted to oppose this spring and to open the valve when in operation, an electric circuit, a source of electricity, a pair of contacts in said circuit, spring means for closing said contacts, means for opening said circuit by separating said contacts and overcoming said spring means comprising a diaphragm, a Pitot tube located so as to register the flow of gas within said turbine, said diaphragm responding to the differential pressures established by said Pitot tube and connected to one of the contacts for the purpose described.

5. An ice melting device for a gas turbine which comprises a passage for recycling some of the hot gas in the turbine, a valve in said passage, a spring holding this valve shut, an electric solenoid adapted to oppose said spring and to open the valve when in operation, an electric circuit, a source of electricity, a contact in said circuits, spring means for closing said contact, opposing means for opening said circuit by separating said contact,

comprising a diaphragm, a chamber associated with said diaphragm, a passage from the gas turbine to said chamber to impose the pressure inside the turbine on said diaphragm, said diaphragm being connected to said contact for the purpose described and in which there is a second contact and in which there is also a Pitot tube located so as to register the flow of gas within said turbine, a second diaphragm responding to the differential pressure established by said Pitot tube and connected to the second contact, the second contact being arranged in parallel with the first contact so that each can function independently of the other to admit some of the gas to the entrance of the turbine for melting the ice therein, whenever either the air pressure or the flow of air falls below a predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS 2,404,275 Clark et a1. July 16, 1946 2,435,990 Weiler Feb. 17, 1948 2,469,375 Flagle May 10, 1949 2,482,720 Sammons Sept. 20, 1949 FOREIGN PATENTS 619,390 Great Britain Mar. 8, 1949 

